An alternate system runs on the fog or fine mist injected into the intake air stream. Although several commercial systems are available, growers can assemble and set up their own system utilizing a ruthless piston pump and fog nozzles. The basic components are proven in Fig. 1. A two-stage system managed by a two- stage thermostat allows more water to be applied on excessively warm, bright days. Temperature settings should be 5-10°F apart.

Algae growth in the pads may become a problem that will reduce the effectiveness of the system and result in accelerated deterioration of the pads. The addition of an algaecide to the water supply will help in control.

It really is desirable, especially in hard water areas, to include a wetting agent to the water to obtain additional uniform wetting of the pads. A commercial materials or liquid home detergent at the rate of 2 tablespoons per 100 gallons may be used.

Water for the pads ought to be clean and lower in mineral content to Greenhouse Auto Vent prevent clogging and coating of the pads. A pump, pipes and gutters are accustomed to recirculate the drinking water. A flow rate 113 gallon per minute per linear foot of pad system ought to be provided to make certain adequate wetting.

In the most common coolant system (fan and pad), the fans draw air through wet pads that extend the length of one endwall or sidewall. Aspen and coated cellulose are normal pad materials that usually have life of 1 to 3 years. Approximately one square foot of pad are is needed for 20 square ft of floor area.